Many occupations can potentially expose an individual to electrical arc flash and/or flames. To avoid being injured while working in such conditions, these individuals typically wear protective garments constructed of flame resistant materials designed to protect them from electrical arc flash and/or flames. Such protective clothing can include various garments, for example, coveralls, pants, and shirts. Fabrics from which such garments are constructed, and consequently the resulting garments as well, are required to pass a variety of safety and/or performance standards, including ASTM F 1506, NFPA 2112, NFPA 70E, MIL C 43829C.
Many protective garments have been made from fabrics comprising natural cellulosic fibers, such as cotton. Cotton fibers are inexpensive and fabrics made from such fibers comfortable to wear. However, the use of cotton fibers in such fabrics has many disadvantages. To begin, cotton fibers are not durable. Thus, fabrics made with them have poor wear life and must be replaced unacceptably often.
Furthermore, cotton fibers pose a health hazard to personnel during the fiber spinning and fabric weaving processes. When natural cotton fibers are used to make fabrics and garments, the cotton fibers can be inhaled and over time can cause respiratory problems, which can lead to byssinosis or “brown lung” disease. Work environments where personnel work with natural cotton and are exposed to breathing hazardous cotton fibers are thus subject to governmental and regulatory restrictions for handling and processing of such fibers.
Moreover, cotton fibers are not inherently flame resistant and thus apt to burn. Thus, these fibers (or the yarns or fabrics made with such fibers) have historically been treated with a FR compound to render such fibers (or the yarns or fabrics made with such fibers) flame resistant. Treatment of cotton fibers (or the yarns or fabrics made with such fibers) with an FR compound significantly increases the cost of such fibers (or the yarns or fabrics made with such fibers).
To avoid the cost associated with such FR treatment, cotton fibers have been combined with FR modacrylic fibers. The FR modacrylic fibers control and counteract the flammability of the cotton fibers to prevent the cotton fibers from burning. In this way, the cotton fibers (or the yarns or fabrics made with such fibers) need not be treated with a FR compound.
However, the FR modacrylic fibers have durability problems similar to those of cotton, and thus fabrics made with blends of these fibers have poor wear life. Moreover, both natural cotton fibers and FR modacrylic fibers are relatively unstable after thermal exposure, rendering it difficult if not impossible for fabrics made with only these fibers to pass the requisite safety and performance standards for protective garments. Thus, additional inherently FR fibers, such as aramid fibers, have been added to the fiber blend to impart thermal stability to the blend to ensure compliance of the resulting fabric with the requisite safety and performance standards (e.g., by decreasing char lengths in vertical flame tests of such fabrics).
Because of the presence of cotton fibers, the resulting fabrics still exhibit durability problems and unacceptable wear life. Thus, a need exists for fiber blends that include fibers that are more durable than natural cellulosic fibers such as cotton but that still realize the cost and comfort advantages of cotton in such blends.